To determine the physiologic and metabolic predictors of dependency in older adults we will recruit 300 women aged 75-90 for extensive testing. That data will allow us to address the following specific aims: 1) to specify the relationship between physiological capacity and ability to perform "independence activities"; 2) to define the levels of those specific physiologic capacities that are needed by these women to execute "independence activities"; and 3) to determine the underlying metabolic changes in muscle associated with decreases in VO2max, Vet, muscle strength, and endurance. We will recruit equal numbers of older women without major debilitating disease in each of the four categories: 1) without any functional impairment, 2) with 1-2 Instrumental Activities (IADL/PSMA) impairments, 3) with 3-4 IADL/PSMA impairments, and 4) with 5 or more impairments. Those subjects will undergo testing on four different days. That testing will include a medical history and physical exam, demographic, cognitive and affective testing, Activity of Daily Living and Performance task testing, strength and endurance testing of 11 different muscles and an exercise stress test. An additional randomly selected 25% of the subjects will undergo a fifth day of muscle metabolism and tissue perfusion measurements. Hierarchical regression analyses will allow us to determine which physiologic variables significantly predict ability to perform "independence activities" after moderator variables have been partialled out of the equation. We will determine inflection points for functions between physiologic capacities and "independence activities" to define the specific level of each physiologic capacity needed to perform successfully specific "independence activities". Those results will be used to define physiologic profiles necessary for maintaining or restoring independence. Defining the physiologic determinants of functional independence will eventually permit the development of optimal exercise programs designed to prolong independence in older women.